How did that happen? Referee Ronald Torbert was distracted, according to NFL head of officiating Dean Blandino.

"What the referee was actually doing at that moment, he was correcting a number from a foul on the previous play, and he just didn't recognize [No.] 64 signaling him," Blandino said Tuesday on NFL Network. "We didn't recognize that he reported, and that's why the penalty was called."

Blandino said Urschel did everything correctly, in terms of waving his hands over his uniform number to show he was reporting as an eligible receiver. Urschel caught a 6-yard pass to move Baltimore to the Arizona 7-yard line, but that was negated by the penalty. The Ravens settled for a field goal on the opening drive to take a 3-0 lead over the Arizona Cardinals.

"It's important that the referee recognizes that, and it's important that the player gets the visual signal," Blandino said.

After the Ravens' 26-18 loss, Ravens coach John Harbaugh said he was told by Torbert, who is in his second season as a referee, that he didn't see Urschel declare himself an eligible receiver.

"Yeah, it's self-explanatory," Harbaugh said. "John did everything that he was supposed to do in that situation, just as he was coached. It was a legal formation."

League sources told ESPN's Ed Werder that Torbert will not be punished because that call was determined to not be critical to the outcome of the game.